Efficient power and thermal management system for high performance aircraft

ABSTRACT

A system and method for improved system efficiency of an integrated power and control unit (IPCU) of an aircraft is disclosed. The system uses an open-loop cooling system and turbo machine power matching to provide wide operation range without over-sizing. In order to reduce the temperature of the air flow through the cooling heat exchanger, the cooling turbine need to expand further in the same time generating power but the power could be higher than the compressor could absorb so a generator that would convert the power and used in supplying the aircraft would result in more efficient system.

BACKGROUND

The invention relates generally to electrical power and cooling systemsfor aircraft and more particularly to enabling high energy systemoperation using an integrated power and cooling unit for highperformance aircraft.

Modern aircraft integrate a number of systems to perform the functionsrequired for flight and operation. A propulsion engine provides power tothe aircraft when in flight and also drives the main generator toprovide electrical power, either during flight or when on the ground. Inorder to provide the emergency backup power in the event of main engineor main generator failures, aircraft have evolved to include asupplemental non-propulsion engine such as the auxiliary power unit(APU). Since the cooling system is a major function of an aircraft, ithas been integrated with the APU to provide not only cooling but alsopower in the event that it is required if the main generator systemfailed.

This integrated system (APU and cooling system) is often referred to asan integrated power and cooling unit (IPCU) that not only providespneumatic or electrical power for starting the propulsion engine; italso generates electrical power and provides conditioned cooling air tothe aircraft, both during flight and while on the ground. With theincreasing use of systems having high energy requirements on aircraft,the IPCU can also be used to help meet short term high peak power whenneeded so as to minimize over-sizing the main generator system.

FIG. 1 is a schematic block diagram of portions of an aircraftelectrical power and cooling system. As shown in FIG. 1, a prior artIPCU 100 includes cooling turbine 102, compressor 104, starter/generator106 and power turbine 108, all connected to a common drive shaft 110. Inorder for the IPCU to come up to operating speed, initial startup ofIPCU 100 is driven by starter/generator unit 106 in starter mode usingbattery or ground power. After compressor 104 is capable of providingair for combustion then power turbine 108 generates enough power tosustain the power requirements with the system configured to burn fuelusing combustor 112 and thus, continues to drive the power turbine togenerate power. After IPCU 100 is started in combustion mode, it canprovide electrical power for various aircraft systems through integratedcontrol unit (ICU) 114 which sends the power to integrated power unit(IPU) Bus 115. When in normal flight mode, IPCU 100 is then configuredto provide cooling air by running off of propulsion engine bleed airinstead of power input from burning fuel. This is accomplished by meansof cooling turbine 102, which also provides low pressure cool air to anavionics cooling system. This system includes heat exchangers 116 and118 as well as pump 120. The avionics cooling system is used to providetemperature controlled air flow to the avionics equipment and cabin ofthe manned aircraft, as well as for other needs as understood by one ofordinary skill in the art.

Also in FIG. 1, main engine 122 is shown, together with an engine highpressure spool coupled starter/generator 124 and an engine low pressurespool driven generator 126. High pressure spool starter generator 124 isconnected to engine 122 as well as to an electrical power distributionbus 128 through an inverter control unit 130. Low pressure spoolgenerator (LP GEN) 126 is also connected to engine 122 as well as to anelectrical power bus 132 through generator control unit (GCU) 134.

There are several connections between IPCU 100 and engine 122. Highpressure, warm air from compressor 104 can be directed into fan ductheat exchanger 136 of engine 122 when operating in the cooling air mode.This air can also be directed into combustor 112 to generate more powerby burning fuel and driving the power turbine 108 using valve 148.Compressor 104 also receives ambient air through input 142 whenoperating in ground operating mode or in-flight emergency mode.

FIG. 1 shows a closed loop system, which includes heat exchanger 138that provides pre-cooled engine bleed air to compressor 104. The air iscompressed by the compressor 104 and then cooled by the engine fan airthrough the fan duct heat exchanger 136. An additional heat exchanger140 cools the air provided to the cooling turbine using the relativelycool air returned from the avionics heat exchanger 116. The air isexpanded by cooling turbine 102 to generate very cold air to cool theavionics liquid cooling loop through avionics cooler 116. The coolingcapacity of the system is determined by the exit air temperature and themass flow rate of the cooling turbine. A closed loop system has theadvantage of allowing lower bleed air usage which conserves fuel,however, IPCU system pressure is limited by the compressor 104 pressureratio capability. In other words, in order for the air flow exiting fromcooling turbine 102 to feedback to the compressor 104 through heatexchanger 140, the return pressure has to be higher that the replenishflow from the engine. This pressure is set by the operating parametersof compressor 104 when operating at a high altitude. Often,selector/regulator valves 144 and 146 are used to select the enginebleed air according to the operating altitude. Due to the high pressureratio of the modern engine compressor, this limits the cooling turbine102 discharging pressure and the temperature of the cooling flow.

In contrast, FIG. 2 depicts a prior art open loop system where heatexchanger 140 does not provide an input to compressor 104 but iscontrolled by a venting valve 150 then vented to the ambient condition.This open loop system allows a lower cooling temperature exit from thecooling turbine, which means a higher expansion ratio is available athigh altitude. However, bleed air usage is higher and is limited by theflow and temperature required to cool the avionics. Traditionally, inorder to regulate the flow and the cooling capability, the system exitflow pressure and thus the system operating speed is controlled byplacing back pressure to the cooling turbine using an exhaust controlvalve 150. However, in order to deep discharge the cooling turbine 102,power must be absorbed by compressor or the starter/generator 106 on thesame shaft of IPCU 100. Since this prior art system is not designed touse the starter/generator in generating mode to absorb the power, it isthus incapable of operating economically at a wide range of power andcooling capacities. Specifically, if there is peak power equipment thatonly requires peak power occasionally during the flight mission, thenthe system must be over sized to be capable of providing the maximumcooling capability. Therefore, the system is operating at a much lowersetting and lower efficiency most of the time thus resulting in a lessefficient system. In prior art systems, starter/generator 106 is onlyused during system startup, and not during cooling modes of the system.

Thus, a need exists for an improved integrated power and cooling systemthat is capable of providing efficient peak power and cooling notlimited by the operating pressure of the closed loop system or the bythe power balance required to maintain IPCU 100 main shaft speed usingonly the air control valves of the open-loop system.

SUMMARY

The invention provides improved system efficiency of open-loop coolingsystem and maintained turbo machine power matching resulted in wideoperation range without over-sizing. In order to reduce the temperatureof the air flow through the cooling heat exchanger, the cooling turbineneed to expand further in the same time generating power but the powercould be higher than the compressor could absorb so a generator thatwould convert the power and used in supplying the aircraft would resultin more efficient system.

The invention in one implementation encompasses a system for providingelectrical power and cooling for an aircraft having an engine, thesystem including an integrated power and control unit (IPCU)starter/generator coupled to a shaft, a cooling turbine coupled to theshaft, a compressor coupled to the shaft between the IPCUstarter/generator and the cooling turbine, said compressor having aninput for receiving engine bleed air and an output for dischargingcompressed air while rotating the shaft and a power summing controllerfor coupling power from the IPCU starter/generator to a load of theaircraft in parallel with power from the engine.

In an embodiment, the system includes first and second buses forreceiving power from the engine and coupling the power to one or moreloads, a third bus for receiving power from the IPCU starter/generatorand coupling the power to one or more loads and first and secondcontactors, coupled to the power summing controller, for coupling thethird bus to the first and second buses.

In an embodiment, the first and second contactors further comprise oneor more bi-directional solid state, high power contactors.

In a further embodiment, the system includes a first integrated controlunit (ICU) coupled to the IPCU starter/generator, a first currentsensing unit (CSU) receiving an input from the ICU and a IPCU contactorcoupling the first CSU to the third bus such that the power summingcontroller further comprises a first electrical system distributioncontrol unit (DCU) for controlling at least the IPCU contactor and thefirst and second contactors.

In any of the above embodiments, the system includes a low pressure (LP)generator coupled to the engine, a generator control unit (GCU)receiving an input from the LP generator, a second current sensing unit(CSU) receiving input from the GCU and an LP contactor coupling thesecond CSU to the first bus such that the power summing controllerfurther comprises a second electrical system distribution control unit(DCU) for controlling at least the LP contactor and the first contactorto couple the first bus to the third bus.

In an embodiment, the system includes a high pressure (HP)starter/generator coupled to the engine and a second integrated controlunit (ICU) receiving an input from the HP generator and coupling it to ahigh pressure bus, a third current sensing unit (CSU) receiving inputfrom the second ICU and an HP contactor coupling the second CSU to thesecond bus such that the power summing controller further comprises athird electrical system distribution control unit (DCU) for controllingat least the HP contactor and the second contactor to couple the secondbus to the third bus.

In any of the above embodiments, the system includes or more energystorage devices operatively coupled to the third bus.

In any of the above embodiments, the aircraft is operated as an openloop system.

The invention in one implementation encompasses a method for providingelectrical power and cooling for an aircraft having an engine, havingthe steps of generating power for the aircraft using the engine,generating power for the aircraft using an integrated power and controlunit (IPCU) and summing the power from engine and the IPCU and applyingit to a load of the aircraft.

In a further embodiment, the step of generating power for the aircraftusing an engine further has steps of generating power using a lowpressure (LP) generator and coupling it to an LP bus and generatingpower using a high pressure (HP) starter/generator and coupling it to aHP bus.

In an embodiment, the step of generating power for the aircraft using anIPCU further includes the step of coupling the power to an IPCU bus.

In an embodiment, the step of summing the power includes the steps ofcoupling the low pressure bus to the IPCU bus using one or morecontactors and coupling the high pressure bus to the IPCU bus using oneor more contactors.

In an embodiment, the summing step includes the steps of receivinginputs from the IPCU, LP generator and the HP generator at one or moredistribution control units (DCUs) and controlling the one or morecontactors using the one or more DCUs.

In any of the above embodiments, the one or more contactors furthercomprise bi-directional solid state, high power contactors.

In any of the above embodiments, the aircraft is operated as an openloop system.

In any of the above embodiments, the method includes the step of storingpower generated by at least one of the engine and the IPCU in one ormore energy storage devices.

DESCRIPTION OF THE DRAWINGS

Features of example implementations of the invention will becomeapparent from the description, the claims, and the accompanying drawingsin which:

FIG. 1 is a schematic block diagram of a prior art aircraft engine andintegrated power and cooling unit (IPCU) in a closed loop configuration.

FIG. 2 is a schematic block diagram of a prior art aircraft engine andintegrated power and cooling unit (IPCU) in an open loop configuration.

FIG. 3 is a schematic block diagram of an aircraft engine and integratedpower and cooling unit (IPCU) according to the present invention.

FIG. 4 is a schematic block diagram of a power summing apparatusaccording to the present invention.

DETAILED DESCRIPTION

In one aspect, the invention provides an integrated power and coolingunit (IPCU) with improved peak power generation and cooling capability.A power summing technology is used to enable the cooling powergeneration and the control of the IPCU power balance.

Turning to FIG. 3, an apparatus 300 according to the present inventionis shown. Elements in common with FIGS. 1 and 2 have the same referencenumerals. IPCU 100 of FIG. 3 is in an open loop configuration withengine 122, where the output of heat exchanger 140 is vented to ambientair by means of exhaust control valve 150. Cooling turbine 102,compressor 104, starter/generator 106 and power turbine 108 are alllocated on the same shaft 110, thus requiring power balancing betweenthe elements. In other words, the power required by compressor 104,starter/generator 106, and the drag of the shaft bearing system must beequal to the power generated from the air expansion of cooling turbine102 so that the proper operating speed is maintained.

An additional input from engine 122 to IPCU 100 is provided throughvalve 149. This valve provides for a bleed air driven mode in the eventthat additional power is required to use engine bleed air boost. Valve149 allows the use of engine bleed air from selector/regulator valves144 and 146 to drive power turbine 108 so additional power is added toIPCU shaft 110 for cooling or power generation.

In an embodiment according to the present invention, starter/generator106 is used throughout the operation of the aircraft to support coolinggeneration and power regulation, especially during periods of peakcooling needs. Instead of limiting the discharging pressure of thecooling turbine 102 and the power generated from air expansion bylimiting the air flow through heat exchanger 140 using regulator valve150, excess power added to the system in the form of spinning shaft 110by cooling turbine 102 is diverted by starter/generator 106 ingenerating mode through ICU 114 onto IPU bus 115. The power sum control302 adds the extra power to LP bus 132 while power sum control 304 addsthe extra power to HP bus 128 according to the bus loading conditionsand operating modes and configuration of the entire electrical powersystem.

FIG. 4 shows a block diagram of a power summing apparatus according tothe present invention. Elements in common with FIG. 3 have the samereference numerals. LP GEN 126 is connected to generator control unit(GCU) 134, which moderates the output power of the LP generator 126. GCU134 is connected to current sensing unit (CSU) 402 which senses thecurrent output from LP generator 126 and provides the sensed current tothe point of regulation (POR) 406. POR 406 is placed in the LP generator126 distribution system to measure the voltage of the system and provideit to GCU 134 for voltage control. From POR 406, energy originating fromLP GEN 126 is transferred to BUS 132, then through power distributionsystem contactors 408 to loads 410, which can be any power or electricalneeds in the aircraft. GCU 134 and power distribution system contactors408 receive control signals from the electrical system distributioncontrol unit (DCU) 404.

DCU 404 monitors the electrical system operating modes, generatorconditions, and POR 406 measurements to control the amount of energygenerated from the LP generator 126. In a preferred embodiment,measurements from POR 406 are sent to GCU 134 and communicated with DCU404. Typically, all controllers are on a control network and sharingdata and information. LP generator 126 system DCU 404 also crosscommunicates with IPCU ST/Gen 106 system's DCU 414 and HP ST/Gen 124system's DCU 426 to control the overall system operation. DCU 404 andDCU 414 also jointly control contactor 436 to determine whether of notelectrical bus 132 and bus 115 should be connected to each other asexplained in more detail below.

Similarly, IPCU starter/generator 106 is connected to ICU 114, whichmoderates the output power of the IPCU starter/generator 106. ICU 114 isconnected to CSU 412 which senses the current output from IPCUstarter/generator 106 and provides the sensed current to the POR 416,which is placed in the IPCU starter/generator 106 distribution system tomeasure the voltage of the system. From POR 416, energy originating fromIPCU starter/generator 106 is transferred to BUS 115, then through powerdistribution system contactors 418 to loads 420 and 422, which can beany power or electrical needs in the aircraft. ICU 114 and powerdistribution system contactors 418 receive control signals from DCU 414,which monitors the electrical system operating modes, generatorconditions, and POR 416 measurements to control the amount of energygenerated from the IPCU starter/generator 106.

Likewise, HP starter/generator 124, ICU 130, CSU 424, POR 428, BUS 128,contactors 430, loads 432 and DCU 426 are interconnected similarly.

A key feature of the present invention is found in cross-tie contactors434 and 436. Unlike prior art relay type contactors, which provideoperation on the order of 100 milliseconds, the inventive contactors 434and 436 are, for example, electronic semiconductor switches, controlledby DCUs 404, 414 and 426. These switches operate on the order ofmicroseconds, much faster than prior art relays. This allows near realtime combination of power/energy from LP and IPCU by contactor 436, andIPCU 106 and HP 124 by contactor 434.

Contactor 434 is a bi-directional solid state, high power controllerwhich can be turned on and off in high speed, contrary to conventionalmechanical relays. When contactor 434 is turned on, bus 128 and bus 115are connected to each other and loads 432 and loads 420/422 are able toreceive power from either HP generator 124 or IPCU ST/Gen 106. Even ifconditions are such that contactor 434 is controlled to be in an onstate, it may be opened to maintain system independence for systemsafety. This also limits the IPCU ST/Gen system transient due to peakloads operation from being propagated into the HP ST/Gen 124 system andthus, to avoid impacting the electrical power quality.

Contactor 436 is a bi-directional solid state, high power controllerwhich can be turned on and off at a high speed, contrary to conventionalmechanical relays. When contactor 436 is turned on, bus 132 and bus 115are connected to each other and loads 410 and loads 422 are able toreceive power from either LP generator 126 or IPCU ST/Gen 106. Even ifconditions are such that contactor 436 is controlled to be in an onstate, it may be opened to maintain system independence for systemsafety. This also limits the IPCU ST/Gen system transient due to peakloads operation from being propagated into the LP ST/Gen 126 system andthus, to avoid impacting the electrical power quality.

In an alternative embodiment, one or more energy storage devices (notshown) such as batteries or ultra-capacitors may be connected to bus 115to store the energy generated from IPCU ST/gen 106 when additionalcooling from cooling turbine 102 is generated. IPCU 100 can also beconfigured to receive engine 122 high pressure bleed air to drive thepower turbine 108 to generate additional energy to charge the energystorage devices. In a further alternative embodiment, energy storagedevices connected to bus 115 could also be charged by the LP generator126 since contactor 436 allows the energy to flow from bus 132. Duringthe time during which peak power loads are present, energy storagedevices could be sized to provide the transient power needs andcontactor 436 may be opened to limit the power transient propagated intothe LP Gen 126 system. These two operating modes complement each otherfor efficient energy utilization.

Numerous alternative implementations of the present invention exist.With advent of high power, light weight batteries, the IPCU generationrequirements could be reduced but the cooling function would not betotally replaced. This configuration and principles could also beapplied to power system requires more than two main generators and abackup generators for example multiple-engines aircraft.

The steps or operations described herein are just for example. There maybe many variations to these steps or operations without departing fromthe spirit of the invention. For instance, the steps may be performed ina differing order, or steps may be added, deleted, or modified.

Although example implementations of the invention have been depicted anddescribed in detail herein, it will be apparent to those skilled in therelevant art that various modifications, additions, substitutions, andthe like can be made without departing from the spirit of the inventionand these are therefore considered to be within the scope of theinvention as defined in the following claims.

What is claimed is:
 1. A system for providing electrical power andcooling for an aircraft having an engine, the system comprising: anintegrated power and control unit (IPCU) starter/generator coupled to ashaft; a cooling turbine coupled to the shaft; a compressor coupled tothe shaft between the IPCU starter/generator and the cooling turbine,said compressor having an input for receiving engine bleed air and anoutput for discharging compressed air while rotating the shaft; and apower summing controller for coupling power from the IPCUstarter/generator to a load of the aircraft in parallel with power fromthe engine.
 2. The system of claim 1, further comprising: first andsecond buses for receiving power from the engine and coupling the powerto one or more loads; a third bus for receiving power from the IPCUstarter/generator and coupling the power to one or more loads; and firstand second contactors, coupled to the power summing controller, forcoupling the third bus to the first and second buses.
 3. The system ofclaim 2, wherein the first and second contactors further comprise one ormore bi-directional solid state, high power contactors.
 4. The system ofclaim 2, further comprising: a first integrated control unit (ICU)coupled to the IPCU starter/generator; a first current sensing unit(CSU) receiving an input from the ICU; and a IPCU contactor coupling thefirst CSU to the third bus; wherein the power summing controller furthercomprises a first electrical system distribution control unit (DCU) forcontrolling at least the IPCU contactor and the first and secondcontactors.
 5. The system of claim 4, further comprising: a low pressure(LP) generator coupled to the engine; a generator control unit (GCU)receiving an input from the LP generator; a second current sensing unit(CSU) receiving input from the GCU; and an LP contactor coupling thesecond CSU to the first bus; wherein the power summing controllerfurther comprises a second electrical system distribution control unit(DCU) for controlling at least the LP contactor and the first contactorto couple the first bus to the third bus.
 6. The system of claim 4,further comprising: a high pressure (HP) starter/generator coupled tothe engine; a second integrated control unit (ICU) receiving an inputfrom the HP generator and coupling it to a high pressure bus; a thirdcurrent sensing unit (CSU) receiving input from the second ICU; and anHP contactor coupling the second CSU to the second bus; wherein thepower summing controller further comprises a third electrical systemdistribution control unit (DCU) for controlling at least the HPcontactor and the second contactor to couple the second bus to the thirdbus.
 7. The system of claim 2, further comprising one or more energystorage devices operatively coupled to the third bus.
 8. The system ofclaim 1, wherein the aircraft is operated as an open loop system.
 9. Amethod for providing electrical power and cooling for an aircraft havingan engine, comprising the steps of: generating power for the aircraftusing the engine; generating power for the aircraft using an integratedpower and control unit (IPCU); and summing the power from engine and theIPCU and applying it to a load of the aircraft.
 10. The method of claim9, where in the step of generating power for the aircraft using anengine further comprises the steps of: generating power using a lowpressure (LP) generator and coupling it to an LP bus; and generatingpower using a high pressure (HP) starter/generator and coupling it to aHP bus.
 11. The method of claim 10, where in the step of generatingpower for the aircraft using an IPCU further comprises coupling thepower to an IPCU bus.
 12. The method of claim 11, where in the step ofsumming the power further comprises the steps of: coupling the lowpressure bus to the IPCU bus using one or more contactors; and couplingthe high pressure bus to the IPCU bus using one or more contactors. 13.The method of claim 11, wherein the summing step further comprises thesteps of: receiving inputs from the IPCU, LP generator and the HPgenerator at one or more distribution control units (DCUs); andcontrolling the one or more contactors using the one or more DCUs. 14.The method of claim 15, wherein the one or more contactors furthercomprise bi-directional solid state, high power contactors.
 15. Themethod of claim 9, wherein the aircraft is operated as an open loopsystem.
 16. The method of claim 9, further comprising the step of:storing power generated by at least one of the engine and the IPCU inone or more energy storage devices.